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Evolution of the EEG in children with Rasmussen's syndrome
Francesca Longaretti1, Colin Dunkley, Sophia Varadkar
1Neurosciences Unit, UCL-Institute of Child Health, London, United Kingdom.
Insights
Early diagnosis of Rasmussen syndrome (RS) and focal cortical dysplasia (FCD) is challenging. Electroencephalography (EEG) findings evolve over time, with contralateral abnormalities suggesting RS and cognitive decline.
Area of Science:
- Pediatric Neurology
- Epileptology
- Neurophysiology
Background:
- Rasmussen syndrome (RS) and focal cortical dysplasia (FCD) present diagnostic challenges, particularly in early epilepsy stages.
- Electroencephalography (EEG) is crucial for evaluating pediatric epilepsy but early differentiation between RS and FCD remains difficult.
Purpose of the Study:
- To review electroencephalography (EEG) findings in children with Rasmussen syndrome (RS) and focal cortical dysplasia (FCD) to identify early indicators.
- To compare EEG patterns between RS and FCD at various time points after seizure onset.
Main Methods:
- Retrospective review of case notes and standard EEG recordings of children with suspected RS or unilateral FCD evaluated for epilepsy surgery (1992-2005).
- Comparison of EEG findings at <3 months, 3-6 months, and 3-5 years post-seizure onset.
Main Results:
- In RS, 50% showed background abnormalities <3 months post-seizure, with 80% of these having persistent high-amplitude delta activity over the affected hemisphere.
- By 3-5 years, 62% of RS patients developed independent interictal abnormalities over the unaffected hemisphere, not seen in FCD patients.
- Contralateral interictal abnormalities in RS were associated with significant cognitive decline.
Conclusions:
- No definitive EEG changes at epilepsy onset differentiate RS from FCD.
- Evolving EEG patterns, including persistent delta activity and later contralateral abnormalities, may support an evolving RS diagnosis.
- The development of contralateral abnormalities in RS highlights the risk of cognitive dysfunction.
Purpose:
The early diagnosis of Rasmussen's syndrome (RS) is often difficult, with differentiation between RS and focal cortical dysplasia (FCD) at epilepsy onset problematic. This study reviewed electroencephalography (EEG) in the two conditions for early indicators of either pathology.
Methods:
All children with either suspected RS or with unilateral FCD undergoing evaluation for epilepsy surgery between 1992 and 2005 were identified. Case notes and standard EEG recordings were reviewed. EEG findings were compared where available at <3, 3-6 months, and 3-5 years after seizure onset.
Key Findings:
Nineteen children with RS and 17 with FCD were ascertained. In EEG studies performed <3 months after seizure onset, 50% (5/10) of the RS group showed background abnormalities, with 80% of these (4/5) showing persistent high-amplitude delta activity over the affected hemisphere. This compared to 66% (6/9) of the FCD group with 17% (1/6) showing marked background asymmetry. By 3-6 months after seizure onset, independent interictal abnormalities over the nonaffected hemisphere were seen in 25% (2/8) of the RS group and by 3-5 years in 62% (5/8) compared to none in the FCD group at any time points measured. These independent contralateral interictal abnormalities were notably associated with a significant decline in cognitive skills over time.
Significance:
No specific EEG changes at diagnosis of epilepsy were identified to help differentiate between RS and FCD. Emerging persistent delta activity over the affected hemisphere with contralateral normal background rhythms, followed in due course by independent interictal epileptiform abnormalities over the unaffected hemisphere may support the diagnosis of RS as the condition evolves, and highlight the risk of overall cognitive dysfunction.
